Document DE 10 2009 047 338 describes a device for generating ammonia including a reservoir separated into two portions to form a first central reservoir connected to the exhaust line through control means for releasing ammonia, a metering valve here, and a second reservoir. The first central reservoir has a significantly smaller size than the second reservoir. Each reservoir includes a different ammonia storage element, each element allowing release of the reducing agent following a desorption reaction. The first central reservoir is completely positioned inside the second reservoir and is connected to the latter through a switching valve, such as an anti-return valve.
Further, a heat generating element is positioned inside the first central reservoir.
The first central reservoir and the second reservoir are thermally connected to each other, so that when the heat generating element is activated, heat is also transferred to the second reservoir.
This ammonia generating device has the goal of allowing sufficient resupply with a reducing agent, regardless of the operating state of the vehicle, while limiting the energy required for releasing the reducing agent contained in the storage elements present in the first central reservoir and the second reservoir, respectively.
Such an ammonia generating device is, however, complex to apply and may have uncertain operation notably when the heat produced by the heat generating element is insufficient for allowing the desorption reaction in the second reservoir, for example when the vehicle covers low mileage and when the duration of the powering up of the heat generating element is insufficient.